(1) Field of the Invention
This invention relates to fluid flow measurement and more particularly to the mounting of orifice plates in fluid pipe lines.
(2) Description of the Related Art
The measurement of the flow of fluids by orifices in the pipe lines is old and well known. Tens of thousands of fittings for such have been sold and are in commercial use.
Typically, a fitting for such use includes a structure having an inside diameter equal to and co-axial with a pipe line inside diameter. The fitting will have a seat slot therein by which an orifice plate mounted within a seal ring may be inserted. The ring seal will have an inside annular surface. The orifice plate will fit within a recess in the inside annular surface.
The accuracy of the measurement will be effected by the precision by which the orifice is mounted within the fitting. For example, KENDRICK, U.S. Pat. No. 5,085,250, describes the effect that lack of concentricity of the orifice within the orifice plate to the inside diameter of the fitting will have. KELLETT, U.S. Pat. No. 1,958,854 recognizes the desirability of having a uniform inside diameter along and adjacent to the orifice plate itself.
Recent changes have been made by the API 14.3 specifications of orifice seal ring protrusion and recess tolerances. I.e., the variations in the protrusions or recesses can affect the accuracy of the flow determination within the pipe line.